I think Bill Simmons linked to this in his "uber links" page. If you look at Canseco, the guy is blinking like crazy. That cracked me up. My other favorite is Mo Vaughn from the Red Sox batting stances video...

One of my favorites that wasn't in there was Tony Phillips. I remember one time playing baseball in my freshman of high school. I was behind the count at 0-2. I decided to get down into a Tony Phillips stance to get the count back into my favor. I bent my right leg as much as possible, extended my left leg as far out as possible. At this point, I was as far down as you can get without falling to the ground. I forced the guy to throw strikes; as a result, I drew a walk thanks to the Tony Phillips stance. Thanks Tony, I'll always appreciate your contribution.